Coalescing filters are used in applications to remove liquids, such as water or oil, from fluids. Typically, such filters are located downstream of a vessel or cylinder containing the fluid, such as air or gas. Because of the large pressure differential that may exist between the interior and exterior of the filters, coalescing type filters are typically provided with a rather thick-walled filter housing that is costly to manufacture. Because of limited available space, however, the filter housings are usually relatively small and as a result, frequent servicing of the filters is typically required to drain off coalesced liquids.
A coalescing type filter is designed to remove oil and water aerosols by means of coalescence. That is, small droplets of moisture or oil adhere to a filter medium and coalesce into larger liquid droplets that can be collected and removed from the filter. Flow through the filter is usually from an inside chamber to an outside chamber though the alternate is also possible.
In general, coalescing filters embody two separate chambers that are at different pressures, such that the pressure differential directs flow of a gaseous stream from a region of higher pressure to a region of lower pressure. In many cases, the two chamber design of coalescing type filters results in the accumulation of liquid within each separate chamber and engineering challenges remain in removing accumulated liquid from either chamber without re-introducing the removed liquids back into the gas stream.
Therefore, there is a need to provide an apparatus and method for removal of liquid from a coalescing-type filter from two separate chambers at two different operating pressures. It is also preferable to provide a method and apparatus for removing liquid at two locations at two different pressures simultaneously.